This invention relates to improved explosives that contain water. In particular the invention provides for the addition of zinc salts to stabilize water-containing explosives that require largely siliceous or borosilicate microspheres that tend to be reactive.
Slurry, emulsion and gelled explosives contain an inorganic oxidizing salt, a carbonaceous fuel source and a vehicle, usually water, with materials required to provide the desired rheology. Such explosives also require additional ingredients to assure detonation. U.S. Pat. No. 3,456,589, among many others, suggests that hollow glass microspheres when added to slurry explosives provide enhanced sensitivity. Such glass microspheres often contain boron and are alkaline. These constituents can be leached in the aqueous system so that the pH of the system is raised and the desired rheology is altered. Additional acid may be added to the system to mitigate these problems; however, the glass microspheres are often degraded and become filled with liquid. Liquid filled microspheres do not sensitize these explosive systems. Hollow microspheres with shells of silicate and polysalt are described in U.S. Pat. Nos. 3,794,503 and 3,796,777. These microspheres do not have fused shells and are more sensitive to the aqueous environment. The shells of the silicate-polysalt microspheres are strengthened and rendered more water resistant by exposure to multivalent metal ions as described in U.S. Pat. No. 4,340,642. Although such microspheres remain intact in water-based explosives they still tend to contribute sufficient boron and alkali to cause undesirable changes.
It is an object of this invention to provide stable water-based explosives that contain alkaline hollow microspheres as sensitizers, said microspheres having shells that contain alkali, silica and boron.